Method of producing selenium rectifiers or the like



Oct. 3, 1939. F. BRUNKE 2,175,016

METHOD OF PRODUCING SELENIUM RECTIFIERS OR THE LIKE Filed June 55, 1937 Fig. I.

cou/vrzre ELECTRODE.

gag/ 444 44140155; wgllllqgwaqlllln MIXTURE 0F VAPOR/ZED CQUNTER E L EC TRODE M/XTURE 0F VAPOR/2E D 24 !(4 114 144 4444 14444- wlawawaa 4 55L E/V/UM AND METAL up ALLOY OF THE 4 aeou co/vs/smva 0F ALUM/NUM, MAGNESIUM AND BERYLL/UM.

Inventor: Frit z Brunke is Attorneg.

Patented 3, v I

'METHOD OF PRODUCING sELENIUM FIERS on LIKE THE FFlCE RECTI-,,

Fritz Brunke, Berlin-Steglitz, Germany, asslgnor to General Electric Company, a corporation of New York Application June 3, 1937, Serial No. 148,318

Germany June 20, 1936 9 Claims.

My invention relates to dry plate rectifiers or like devices such as light-sensitive cells of the type'wherein a semi-conductor layer composed of a material such as selenium or a selenium compound is deposited by a vaporization process on a carrier electrode. The object of the invention is to provide an improved device of the above type and an improved method of forming the semi-conductor layer on the carrier electrode.

Conventional cells; 01' the selenium type for rectifiers or light-sensitive devices comprise a carrier electrode ghaving thereon a semi-conductor layer of selenium or selenium compound, and a counterelect'rode in contact with the semi conductor layer. I-Ieretofore the semi-conductor layer has been commonly produced by a mechanical application of the selenium or selenium compound to the carrier electrode, for example by melting of the semi-conductor material upon the electrode and flowing the material thereover to form a layer of the required thickness. It has been suggested to produce the semi-conductor layer, for cells of the selenium type for example, by exposing the carrier electrode to the vapor of a semi-conductor material in a high vacuum.

Semi-conductor layers produced by the latter or similar vaporization methods are characterized by a more uniform construction and greater degree of emciency as compared with layers pro duced by the mechanical methods such as the above-mentioned fusion of the semi-conductor material to the carrier electrode. Light metals, or metal alloys, for example metals or alloys oi the group comprising aluminum, magnesium and beryllium, have proved to be particularly advantageous and efficient materials for the carrier electrode when the vaporization method of iorming the semi-conductor layer is employed.

- The vaporization method has had the disadvantage, however, that the carrier electrode must be maintained at a temperature at which the semi-conductor material has a low vapor pressure. Thus a condition, not easily controlled, of the semi-conductor material ensues in which the material may be at a given instant either in process of being condensed or of being vaporized, and the thickness and structure of the semiconductor layer obtainable are so greatly dependent on the temperature or the carrier electrode and on the vapor pressure of the semiconductor emerging from the vaporization apparatus that these characteristics 01 the semiconductor layer can not, arbitrarily, under this latter condition, be properly determined. In the use of the vaporization process other difliculties connection with the accompanying drawing and its scope will be pcintedout in the appended claims.

Referring to the drawing, Figs. 1 and 2 illustrate rectifier cells in which, in accordance with my invention, a semi-conductor layer is mounted between a carrier electrode and a counterelectrode.

In Fig. I the rectifier cell or element includes a carrier electrode I, a semi-conductor layer 2, and a counterelectrode 3. The semi-conductor layeris deposited on the carrier electrode by exposing the carrier electrode to the vapor of a semi-conductor material, as usual in the vaporh zatlon process. In accordance with the present invention, however, the vaporizing-of the semiconductor material and the exposing of the carrier electrode i to the vapor or the material, for forming the semi-conductor layer 2, on the carrier electrode, take place in an atmosphere of a neutral gas. Nitrogen and the rare gases, helium, neon, argon, krypton, and xenon have proved suitable. In accordance with the method of the present invention the thickness and structure of the semi-conductor layer can be better controlled than by former methods; by varying the pressure of the neutral gas and the temperature of the carrier electrode within wide limits, adjustment can be made for any especial condition arising from the revaporization of the semi-conductor material.

The method in accordance with my invention can further be improved by employing a directed stream of the neutral gas, thus hindering the revaporization, of the semi-conductor material which is being deposited onto the carrier electrode. The gas current is preferably caused to flow directly against the carrier electrode, so that thelosses of material become small. Preheating of the current of neutral gas has proved to be of advantage.

The method according to the present invention makes it possible that a plurality of semi-conductor materials may be simultaneously vaporized and intermixed without difliculty, the semiconductor layers thus obtained proving very emcient in many cases. The production of such compound layers has been difiicult heretofore by reason of the varying gas pressure of the components in the course of evaporation in a high vacuum, whereas the presence of a neutral gas, asv provided by my present invention, considerably improves and simplifies the method or production of the semi-conductor layer. the use of the neutral gas, and by carefully directing the gas stream against the carrier electrode, eificient mixing of the components of the semi-conductor material is assured. I have found that a mixture of selenium and iodine, as illustrated in Figs. 1 and 2, is particularly advantageous.

When employing the method of the present invention it is, further, expedient to operate at a pressure of the neutral gas which is higher than the external-pressure, i. e., at a pressure higher than one atmosphere, the neutral gas then preventing access of air to the carrier electrode, upon which the semi-conductor layer is being deposited. By this means, further, an especially favorable condition is possible and preferably.

utilized for developing the semi-conductor layer, viz., the maintaining of the carrier electrode, upon which the layer is being deposited, at a temperature of over 210- C.

In Fig. 2 the semi-conductor layer 2 is composed, as in Fig. 1, of a mixture of selenium and iodine. The carrier electrode 4, however, is composed of a metal or metal alloy of the group comprising aluminum, magnesium and beryllium. The semi-conductor layer is deposited on the carrier electrode in the same manner as hereinabove described in connection with the cell or element illustrated in Fig. 1.

It has been set forth herein that light metals or alloys are suitable as materials for the carrier electrode. It will be readily understood, however, that other well known materials such as iron or nickel may be utilized for this purpose in practising my present invention.

My invention has been described herein in particular embodiments for purposes of illustration. It is to be understood, however, that the invention is susceptible of various changes and modiiications, and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

What I claimas new and desire to secure ,by Letters Patent of the United States, is:

1. The method of producing an element for a dry plate device, said element comprising a carrier electrode composed of a material of .the

group comprising aluminum, magnesium, and beryllium and alloys of said metals, which includes exposing said electrode to a mixture of selenium vapor and iodine vapor in the presence of a chemically neutral gas.

2. The method of producing an element for a dry plate device, said element comprising a carrier electrode, which includes forming a vapor of a semi-conductor material, forming a current of preheated, chemically inactive gas, and blowing said vapor against said carrier electrode by said current of gas, to form a layer of said semiconductor material on said electrode.

3. The method of producing an element for a dry plate device, said element comprising a carrier electrode, which includes exposing said electrode to the vapor of a semi-conductor material in the presence of a chemically neutral gas, said gas being at a pressure higher than atmosphere, and maintaining said carrier electrode at a temperature sufficiently low to cause said vapor to condense thereon to form'a solid semi-conductor layer thereon.

4. An element for a dry plate device, including a carrier electrode, and a semi-conductor layer on said electrode composed of a mixture of selenium and iodine.

5. An element for a dry plate device, including a carrier electrode composed of a material of the group comprising aluminum, magnesium, and beryllium and a semi-conductor layer on said electrode composed of a mixture of selenium and iodine.

6. An element for a dry plate device, including a. carrier electrode composed of an alloy of the group of metals comprising aluminum, magnesium and beryllium, and a semi-conductor layer on said electrode composed of a mixture of selenium and iodine.

7. The method of producing an element for a dry plate rectifier or the like, said element comprising a carrier electrode composed of a material of the group comprising aluminum, magnesium, and beryllium and alloys of said metals, which includes exposing said electrode to a mixture of selenium vapor and'iodine vapor in the presence of a chemically neutral gas.

8. An element for a dry plate rectifier or the like, including a carrier electrode, and a semiconductor layer on said electrode composed of a mixture of selenium and iodine.

9. An element for adry plate rectifieror the like, including a carrier electrode composed of a material of the group comprising aluminum, magnesium, and beryllium and alloys of said metals, and a semi-conductor layer on said electrode composed of a mixture of selenium and iodine.

FRITZ BRUNKE. 

